This invention relates to a torque-actuated expansible shaft assembly for insertion into a paper roll core or other sheet roll core. The shaft assembly may constitute either a relatively short chuck for insertion into the end of a core, or a much longer shaft assembly extending completely through the core from end-to-end.
During manufacture of paper or other sheet products, the sheet material is typically wound onto, or unwound from, a tubular core supported by a diametrically-expansible shaft assembly insertable into the core and selectively actuated so as to expand into engagement with the core for transmitting either driving torque or braking torque to the core. Most conventional expansible roll core shaft assemblies employ core-engaging elements actuated either by means of pneumatically-expandable elements or by means of internal torque-actuated cams. Examples of pneumatically-actuated shaft assemblies are shown in U.S. Pat. Nos. 4,147,312 and 4,771,963. Examples of torque-actuated-cam shaft assemblies are shown in U.S. Pat. Nos. 2,528,873, 2,561,745, 3,332,694, 3,623,741, 3,774,921, 3,792,868, 3,963,250, 3,993,317, 4,193,633, 4,334,652, and 4,519,620. All of these shaft assemblies require complex internal structures for actuating the core-engaging elements to cause them to expand into engagement with the core, such structures being relatively expensive to fabricate, in need of frequent servicing, and highly susceptible to wear. Moreover, the cam-actuated shaft assemblies can develop significant friction at their camming surfaces which, if the actuating torque is high, can lock the cams making it difficult to disengage the shaft assembly from a core.
Other types of previous core-engaging shaft assemblies include those employing rocker-type lugs pivotally mounted on a shaft for pivoting outwardly into engagement with the interior of a core in response to the application of torque to the shaft. Examples of these shaft assemblies are shown in U.S. Pat. Nos. 3,001,736, 3,018,977, 3,146,964, and 3,281,092. These shaft assemblies do not need cams, because their lugs are actuated in response to torque applied through the shaft directly to the pivot axes of the lugs rather than through cam surfaces, and therefore do not suffer from the same frictional disadvantages and complexities of torque-actuated-cam assemblies. However, these latter shaft assemblies do suffer from a major disadvantage in that they are incapable of being actuated bidirectionally automatically in response to reversals of torque while remaining inserted in the core. Some of these assemblies, such as that shown in U.S. Pat. No. 3,281,092, can be adapted to apply torque to the core in a reverse direction but only by withdrawing the shaft assembly from the core and reconfiguring it mechanically. Others, such as that shown in U.S. Pat. No. 3,018,977, can apply torque to the core bidirectionally because they are locked in an engagement position, but such locking prevents them from being actuated bidirectionally in response to reversals of torque, which in turn prevents them from releasing from the core automatically in response to the absence of such torque to enable their quick removal from the core. Moreover, the torque-actuated lugs of these shaft assemblies require a relatively large angular pivoting motion to accomplish core engagement in response to applied torque, which can make the core engagement too slow. In addition, the continuous extension of the lugs axially along the shaft assembly significantly impairs the beam strength of the assembly.